One Thursday night in early July, Chanel Celaya was home in LA packing for a trip when she got a call. She dropped everything at the sound of two magical words: Justin. Bieber.

At 20, the model and occasional actress had landed the role every 12-year-old girl dreams of: the love interest in the teen pop star’s latest music video, for “As Long as You Love Me.”

Celaya, who started modeling at age 13, was already a fan of Bieber’s, though hardly the obsessive kind. But she had turned his tune “Never Say Never” into a kind of personal anthem. “When I was working out, it was really a very motivational song because it made me run faster,” she recalls. “I’m like, ‘You’re right — never say never!’ ”

Her cameo in the video quickly brought Beliebers to her side. Once it came out Aug. 1, her social media stock shot through the roof. She went from having 300 followers on Twitter to nearly 15,000. Her name turned into a worldwide trending topic.

“OK, not gonna lie, I didn’t even know what trending meant,” she laughs. “Someone was like, “Yeah, your name is trending!” and I was like, ‘Is that good?’ ”

It’s the Bieber effect, also experienced by Carly Rae Jepsen, who landed atop the Billboard Hot 100 after a Justin shout-out.

“After shooting, everyone was like, you know, his fans are the best fans in the world, but be careful because they may not like you and they may be mean to you,” she says. But instead of the rabid attack-dogs that came after Selena Gomez when she stole the “Baby”-boy away from tweens everywhere, Celaya found only support.

Maybe the Beliebers are growing up. Or maybe they just like living vicariously through Celaya, who locked lips with the heartthrob over and over again on set.

“He definitely had minty fresh breath,” she says, adding, “I brushed my teeth before every scene. I had mints, gum, everything. I think he had the same concept and courtesy of doing that.”

Tell us more, Chanel.

“He did smell very good,” she laughs. “I have no idea what he was wearing, but I remember being like, ‘Wow, you smell really good.’ ”

Is the Biebs attentive to a lady?

“If I was standing off to the side, he was like ‘Get over here. Come talk to us!’ ” she says.

And what does the world’s biggest male pop star talk to a beautiful young woman about?

“I mean, just normal things,” she says. “What’s your favorite color? Favorite food? Favorite animal? Just normal things you’d ask after making out with someone, I guess,” she laughs.

After modeling stints with

everyone from Guess to Nordstrom, Celaya hopes the Bieber boost will take her to the next level. She made her big-screen debut this spring with a small role in “21 Jump Street” as — who else? — a cringing hot chick who not-so-politely turns down Jonah Hill’s prom request.

This fall, she’ll appear on teens’ screens with a guest-starring role on MTV’s adaptation of the British hit “The Inbetweeners.” She’s currently auditioning for several movies and TV shows, and just finished shooting a new ad campaign.

Despite her frequent lip locks with Bieber, she’s hasn’t stayed in touch with him. She doesn’t have his cellphone number and never even asked if he might call her, maybe.

“That’s a no-no! He’s got a girlfriend!” she says. “You don’t do that.”